A wide variety of friction sheet feeding machines are available for feeding individual sheets from the bottom of an essentially vertical stack of sheets. These machines typically include a friction retard surface positioned above a driven friction roller.
Friction retard surfaces have a wide variety of sizes, shapes, contours, coefficients of friction, etc. Friction retard surfaces have been employed over the years, in a rotating fashion, with the retard roller rotated in a forward direction on some machines, and rotated in a reverse direction in others. While a forward rotating friction retard roller provides significant advantages when feeding certain types of sheets, such as course flat product, and a reverse rotating friction retard roller provides significant advantages when feeding other types of sheets, such as coated, glossy, printed product, the direction of rotation limits the types of sheets which may be reliably fed through the friction sheet feeding mechanism.